This invention relates generally to the art of electron beam accelerators and more particularly to the art of cooling such electron beam accelerators.
Electron beam accelerators are used in a variety of environments. The most readily known environment is that of cathode ray tubes which in and of themselves have an extremely diverse variety of applications.
While cathode ray tubes maintain accelerated electrons within the environment of the tube enclosure, applications exist for electron accelerators where the electrons must pass through a window for further utilization. Examples of this are applications such as crosslinking and grafting of polymeric materials, the curing of coatings and inks, the pasteurization of food stuffs or the sterilization of medical products wherein the electrons pass through a thin foil window to reach the product treatment area.
Windows utilized in conventional electron beam accelerators in such applications are generally formed of a foil which is reasonably transparent to an electron beam. Generally such foils are formed of titanium or titanium alloys that are very thin, e.g. approximately 0.4 to 1.5 mils in thickness. In particular, a preferred alloy is formed of 96% (weight percent) titanium with 3% aluminum and 1% vanadium.
When such windows are contacted by the accelerated electrons, a significant portion of the electron energy is imparted to the window resulting in heating thereof. This heat must be removed from the thin foil window or the window will overheat and melt resulting in catastrophic failure of the electron beam accelerator.
Currently such windows are cooled by one of two methods. Water cooled support structures which are either ribbed or perforated cool the window by conduction. Such conduction cooling, however, has not been totally satisfactory since the windows have relatively short lives.
A more effective method of window cooling utilizes a high velocity jet of air which passes over the exterior window surface. Windows cooled in this manner have long service lives, but there is a problem associated with the production of ozone when such air is irradiated by the electrons passing therethrough.
There is thus a significant need for improvement with regard to the cooling of electron beam accelerator windows.